Abstract Book

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ESTRO 37

Table 2 : Results of goodness of fit chi-squared (χ 2 ) test.

Results In a day after radiation exposure by 10 Gy and 40 Gy a decrease of SHG signal intensity in bladder as well in rectum was observed (Fig. 1a,b). In a week, SHG signal intensity remained essentially decreased. In a month after irradiation, we observed a retrieval the signal intensity to the initial level after 10 Gy exposure and a lack of recovery after 40 Gy exposure. In case of 2 Gy exposure, there was no significant changes independently on time after irradiation. Similar changes were observed by studying the organ samples ex vivo by CP OCT (Fig.2 a,b). Statistical relationship analysis showed a high positive correlation between the mean SHG signal intensity and the mean IDF of bladder (r xy = 0,855, р<0,005) and rectum (r xy = 0,813, р<0,005). Conclusion High positive correlation between the mean SHG-signal intensity and the mean IDF of bladder and rectum indicate that CP OCT can be used for non-invasive estimation of extracellular matrix radiation damage. 1. E. Kiseleva et al. Differential diagnosis of human bladder mucosa pathologies in vivo with cross- polarization optical coherence tomography. Biomed Opt Express. 2015; 6(4): 1464–1476. EP-2277 Apoptosis and injuries of heavy ion beam and x-ray radiation on malignant melanoma cells S. Li 1 , J. Qin 1 , C. Zhang 1 1 Lanzhou General Hospital of PLA, Department of Radiotherapy, Lanzhou, China Purpose or Objective This study aims to investigate the influence of high linear energy transfer (LET) heavy ion ( 12 C 6+ ) and low LET X-ray radiation on apoptosis and related proteins of malignant melanoma on tumor-bearing mice under the same physical dosage. Material and Methods C57BL/6 J mice were burdened by tumors and randomized into three groups. These mice received heavy ion ( 12 C 6+ ) and X-ray radiation under the same physical dosage, respectively; their weight and tumor volumes were measured every three days post-radiation. After 30 days, these mice were sacrificed. Then, median survival time was calculated and tumors on mice were proliferated. In addition, immunohistochemistry was carried out for apoptosis-related proteins to reflect the expression level. After tumor-bearing mice were radiated to heavy ion, median survival time improved and tumor volume significantly decreased in conjunction with the upregulated expression of pro-apoptosis factors, Bax and cytochrome C, and the downregulated expression of apoptosis-profilin (Bcl-2, Survivin) and proliferation- related proteins (proliferating cell nuclear antigen). Results The results indicated that radiation can promote the apoptosis of malignant melanoma cells and inhibit their proliferation. This case was more suitable for heavy ion ( 12 C 6+ ). High LET heavy ion ( 12 C 6+ ) radiation could significantly improve the killing ability for malignant melanoma cells by inducing apoptosis in tumor cells and inhibiting their proliferation. Electronic Poster: Radiobiology track: Radiobiology of proton and heavy ions

Conclusion The ability of the NTCP models to predict RP was highly dependent on parameter selection, demonstrating that it is difficult to rely solely on these models when making clinical decisions. The dose summary measures MLD, V 10 and V 5 were useful in predicting RP. EP-2276 Quantitative evaluation of collagen damage and remodeling after gamma-irradiation by optical methods M. Kochueva 1 , S. Kuznetsov 2 , V. Dudenkova 3 , A. Varlamova 4 , A. Maslennikova 5 1 Nizhny Novgorod State Medical Academy, Department of Oncology, Nizhni Novgorod, Russian Federation 2 Nizhny Novgorod State Medical Academy, Department of Pathological Anatomy, Nizhny Novgorod, Russian Federation 3 Nizhny Novgorod State Medical Academy, Laboratory of fluorescence bioimaging, Nizhny Novgorod, Russian Federation 4 Lobachevsky State University, Department of Biophysics, Nizhny Novgorod, Russian Federation 5 Nizhny Novgorod State Medical Academy, Department of Oncology, Nizhny Novgorod, Russian Federation Purpose or Objective Damage of extracellular matrix is known to play an important role in the development of adverse events in normal tissues after radiation exposure. The study objective was the quantitative evaluation of the dose- time dependences of bladder and rectum collagen changes after gamma-irradiation by laser scanning microscopy (LSM) with second harmonic generation and cross-polarization optical coherence tomography (CP- OCT). Material and Methods Rat’s bladder and rectum were irradiated (1.25 MeV, Co 60 ) by single doses of 2 Gy, 10 Gy and 40 Gy by a local field (18 animals total). LSM-imaging of deparaffinized slices of bladder and rectum was performed in a day, a week and a month after irradiation by LSM 510 Meta (Carl Zeiss, Germany). Excitation was implemented at 800 nm and registration at 362-415 nm (second harmonic generation of collagen). For quantitative evaluation, a mean intensity of collagen SHG signal was calculated. Calculations were performed by ImageJ 1.39p (NIH, USA). All calculated indexes were normalized to a mean intensity signal of non-irradiated bladder and rectum samples. Cross-polarization optical coherence tomography (CP OCT) is a noninvasive modality for imaging biotissues with micron-scale spatial resolution that allows evaluation of collagen state in vivo and ex vivo by calculation the Integral Depolarization Factor (IDF) [1]. A spectral domain OCT system (IAP RAS, Nizhny Novgorod, Russian Federation) operating at 1.3 µm central wavelength with axial resolution of ~10 µm and lateral resolution of ~15 µm was used.